A prosecutor in Champaign County made several missteps when trying to perfect the impeachment of a defense witness with a prior inconsistent statement during Travis Lewis’ aggravated battery trial.Lewis allegedly grabbed Valisa Byndum’s cellphone, started deleting text messages he didn’t want his girlfriend to see and choked Byndum for several seconds.Going into the trial, the prosecutor had a written report from Justin Prosser, a Champaign police officer, that said one of the eyewitnesses — Lewis …